As I'm sure others will soon mention, speaker placement, set up and source material are very important. Make sure the M80's are at least 12 inches away from the back wall, 18" would be better. It takes some tweaking to get everything set up properly.
Poorly recorded music will sound poor no matter how good the system. Make sure you are using source material that is of high quality. For movies, try The Incredibles, track #9.
16ga speaker wire is thinner than I would use, but should make very little difference if the runs are short, less than 12 feet or so.
